The present invention relates to an engine control system for electromagnetically operating intake and exhaust valves of an internal combustion engine.
In gasoline engines, the amount of intake air to be introduced into engine cylinders is controlled by a throttle valve disposed in an intake pipe and operated by an accelerator pedal.
Since the engine cylinders are spaced a large distance from the throttle valve disposed in the intake pipe, the response of the engine to the operation of the accelerator pedal is relatively slow. Inasmuch as the throttle valve is disposed in the intake pipe, as described above, a vacuum developed in the intake manifold, and hence the pressure in the intake manifold is lowered. Therefore, the temperature in the intake manifold is considerably low in a cold climate. When the ambient temperature is low, fuel injected into the intake manifold by a fuel injection valve is not atomized well. Such poor atomization of the fuel is one of the reasons for inefficient fuel combustion at low temperatures.
Electromagnetic valve control systems for controlling the timing of operation of the intake and exhaust valves of internal combustion engines through an electromagnetic actuator means are disclosed in Japanese Laid-Open Patent Publication Nos. 58(1983)-183805 and 61(1986)-76713. These publications only show the operation of the intake and exhaust valves with the electromagnetic drive means. The disclosed electromagnetic valve control systems cannot solve the above problem because the amount of intake air is controlled by the throttle valve disposed in the intake valve.